<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
	</body>
	<script>
		//总结 字符串的处理用parseInt()  其他用Number
		     //number 有点是null 和"" 都可以转成 0 而"123px"则转不了123
			  //parseInt() 可以转字符串的单是 Null 和 "" 都是NaN
		/* var a ='123';
		//console.log(a);
		a=Number(a)
		//console.log(typeof a);
	    var b =null;
		console.log(typeof b);
		b=Number(b) //b=0
		console.log(b);
		var c= undefined;
		 c=Number(c);
		 console.log(c);//NaN
		 var f ='123px'
		 f=Number(f)
		 console.log(f);
		 console.log(typeof f);
		 
	  var d= undefined
	  d=parseInt(d)
	  console.log(d);
	  console.log(typeof d);
	  var e =null
	  e=parseInt(e)
	  console.log(e);
	  console.log(typeof e); */
	  
	  /* 首位是字母  null undefined 都是NaN
	   var p ='aa123.99px';
	  p=parseFloat(p)
	  console.log(p);
	  console.log(typeof p); 
	  
	*/
    //减乘除的隐式转换
   /* 
      1/"a"  NaN
	  isNaN(a)  true false
   */
	 
	</script>
</html>
